1. Field of the Invention
The present invention relates to a memory arrangement for information on recording medium, and in particular to such improvement of an IC card that information may be efficiently stored into a memory.
2. Description of the Prior Art
Owing to high density packaging techniques and the like in recent years, respective memory devices have large storage capacities. However, there is a limit in the number of memory devices which can be mounted on an information recording medium such as an IC card. Storage of a larger amount of information and more functions than before are demanded. The amount of information stored thus increases steadily.
Information stored in a memory portion of an information recording medium such as an IC card is classified broadly into information which should be necessarily recorded on each IC card (fixed item information), information selectively recorded according to the purpose or application, and information arbitrarily recorded (variable item information).
In an information recording scheme for an IC card, a memory section for storing data or programs therein is divided into records respectively having fixed information lengths. Further, information inputting/outputting and error detection of recorded information are performed while taking a record as unit. In another information recording scheme, an arbitrary length is chosen to be a record according to the length of information recorded in the memory section. Also, information having variable length is accordingly stored, inputted and outputted. In this case, error detection of recorded information is performed while taking the variable record as a unit.
In the former case, error detection of recorded information can be performed easily. If the record length is detected and error detection of information recorded in the record is performed. However, areas of the memory section are unadvantageously wasted. On the other hand, the latter case has a drawback in that the amount of error detection information increases and the efficiency of use of the memory portion is lowered when the record length is extremely short. This is because error detection information for performing error detection of recorded information is added to each record.
FIG. 1 shows an example of a memory map of such prior art used in an IC card. A fixed item information storage area 3 and a variable item information storage area 4 are provided. Fixed item information and variable item information are continuously stored in respective storage areas. Error detection information is inserted at intervals of a fixed length. Assuming now that the recording information length (word length) of a memory 1 per line is 32 bytes. Fixed item information pieces 5 to 13 are handled while taking 32 bytes as unit a irrespective of the length of the information piece. Also error detection information 2 is recorded at the last position of 32-byte word.
Therefore, each of the fixed item information pieces 7 and 9 are divided by the error detection information and relates to two error detection information pieces.
It is now assumed that an error is caused in the fixed item information 5, which has been recorded, such as a secret identification number. The error is detected from the error detection information 2 of the fixed item information (secret identification number). Since the pertinent error detection information is common to the fixed term information 6 and the fixed term information 7, however, these are also judged erroneous and so processed.
On the other hand, transaction history information 14, stored in the variable item information storage area 4, differ in information length of one information unit, and a number of information units, according to the purpose and application. Accordingly, there occurs a difference in the recording efficiency of memory among IC cards which are different in purpose and application. The efficiency is thus lowered according to the purpose and application.
Any information stored in the fixed item information storage area 3 is very important to the operation of the IC card.